Many child-resistant closures have been developed in recent years, some of them consisting of two cooperating parts, viz. an inner screw-type closure and an outer overcap which can be utilized to turn the inner cap onto the neck of the container but cannot be utilized to remove the cap from the container without special manipulation. These have been relatively expensive because of the necessary two separate parts and the requirement for assembly of those parts. Other types have consisted of single unitary pieces each of them consisting of a cap which is threaded to mate with the threads on the neck of a container in order that it may be screwed downwardly to liquid tight positon and others also unitary in construction but consisting of double skirted elements, the inner skirt having the thread for mating with the container thread and an outer skirt. In these types of containers, the cap usually has one of two cooperating elements which render the cap child-resistant. This may be attached directly to a single skirt cap for cooperation with an element on the container itself or, in a double skirt cap, the child-resistant element is part of the outer skirt and cooperates with an element on the container itself.
Various ways of disengaging the child-resistant elements have been suggested. In some instances, the outer skirt of a two-part cap is lifted to disengage the elements; in others the outer skirt is squeezed inwardly at appropriate places in order to bulge the skirt outwardly to disengage the child-resistant elements. In some of the single skirt caps the child-resistant elements on the cap must be lifted to free it from the locking means on the container. While many of these are effective for child-resistant applications, some of them are so difficult as to require the use of both hands to actuate the child-resistant means while the container is held in some other fashion so that, after disengagement of the child-resistant locking means, the cap can be removed. This is particularly true when older children or even adults with little strength in their hands attempt to open such containers.
It is therefore the principal object of the instant invention to provide a child-resistant locking means for a "twist-action" cap, i.e., a cap having continuous threads which mate with threads on the neck of the container, a cap having discontinuous threads on the container neck, a cap having bayonet-type lugs for mating with lug-threads on the neck of the container or any other type of child-resistant cap which requires a "twist-action" to place it on the container neck as well as to remove it from the container neck in order to gain access to the contents.